The present invention relates to a pole bushing for batteries, particularly of the kind leading through the battery cover and forming a seal between the cover and the battery post.
Such bushings comprise a metal sleeve which is provided with grooves and which is embedded in a sealing material to form a sealing element with an external surface which bears against the battery cover and with an internal surface which at least partially is in close and immovable contact with the post passing through the cover. One end portion of the metal sleeve extends out of the sealing material and forms an annular portion, the internal surface of which forms part of the internal surface of the sealing element and is meant to be at least partially in rigid metallic connection with the post.
A pole bushing for batteries of the kind mentioned above is previously known, for instance from SE-PA No. 7701558-4, and the object with this known device is to provide a pole bushing which can move axially together with the post and simultaneously provide an effective seal between the battery cover and the post. In structures known hitherto, the post, which is rigidly connected via a pole connection to the electrode plates, is also rigidly connected to the battery cover. However, the electrode plates expand due to ageing during operation, thus causing displacement of the post, which could damage the battery cover and result in leakage of the electrolyte. However, these drawbacks have been eliminated with a pole bushing which is displaceable in the cover and provided with means for ensuring a fluid-tight seal between the pole bushing and the cover.
However, the pole bushing according to the Swedish patent application mentioned above is burdened with certain drawbacks, since the material used in the sealing element will only permit an effective seal against the metallic sleeve but not against the battery cover. This means that either the pole bushing or the battery cover must be provided with a recess for a sealing ring made from a material capable of providing an effective seal between the cover and the bushing.
One object of the present invention is to provide a simple structure for a pole bushing by eliminating the recess and the sealing ring and nevertheless maintaining an effective seal between the cover and the bushing.
In accordance with the invention this object is realized by the sealing material having resilient properties and by the external surface of the sealing element being shaped for movable and sealing contact with the battery cover for forming a sealing surface against the cover.
In a suitable embodiment the sealing material is made of rubber, whereas the sleeve and the surface of the post are made of lead.